Which dinosaurs had feathers? Which flew? How scientists know : Short Wave : NPR

Fossil casting of Archaeopteryx, a therapod dinosaur that lived during the Late Jurassic period (around 150 million years ago). Many fossils of Archaeopteryx include impressions of feathers.

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James L. Amos/Getty Images

Fossil casting of Archaeopteryx, a therapod dinosaur that lived during the Late Jurassic period (around 150 million years ago). Many fossils of Archaeopteryx include impressions of feathers.

James L. Amos/Getty Images

When you picture a dinosaur, what does it look like?

Maybe you think of four-legged herbivores like Apatosaurus or Triceratops. Maybe you imagine large armored dinosaurs like Ankylosaurus or Stegosaurus.

But for Jingmai O’Connor, the dinosaurs she studies – look a lot more like birds.

“If you looked at an artist’s reconstruction of something like Velociraptor or Microraptor or a small feathered theropod dinosaur very closely related to birds, you would see that it pretty much looks the same as a bird,” O’Connor says. “I mean, there’s some structural differences in proportions and some minor differences in the skeleton. … But in terms of the plumage, the soft tissues covering the body, it would have looked very, very birdlike.”

O’Connor is a dinosaur paleobiologist and the associate curator of fossil reptiles at the Field Museum of Chicago. She specifically studies theropods, a group of two-legged dinosaurs that includes everything from T. rexes to hummingbirds.

Because yes, birds are dinosaurs, she says. They were the only group of dinosaurs to survive the Cretaceous mass extinction around 65 million years ago (not to be confused with the Permian-Triassic mass extinction that happened some 250 million years ago).

How did those birds survive – and why?

O’Connor calls this question the “million-dollar question of dinosaur paleobiology,” because scientists don’t exactly know.

But one key hypothesis is that birds are simply extremely well-adapted to survive.

“There’s just so many weird things about the physiology of birds, and it’s probably these features that allow them to survive this environmental crisis,” O’Connor says. “They have incredibly efficient respiratory systems. They have an incredibly efficient digestive system that is shorter, more lightweight, more efficient than a mammalian digestive system … they have very elevated metabolic rates and they have these very strange growth patterns.”

O’Connor, for one, is delighted by all of these evolutionary changes researchers can find in the fossil record. It’s a reminder of just how complex evolution can be — and that complexity is part of what makes paleobiology fun.

Have other dinosaur questions you want us to unravel? Email us at shortwave@npr.org — we’d love to hear from you!

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This episode was produced by Hannah Chinn. It was edited by our showrunner, Rebecca Ramirez. The engineer was Jimmy Keeley. Beth Donovan is our senior director and Collin Campbell is our senior vice president of podcasting strategy.

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